Fuel injectors having either ball-valve or disk-valve closures, referred to herein generically as “valves”, are well known. In principle, a disk valve injector configuration is superior to a ball-valve configuration in terms of flow capacity and dynamic range, attributes that are very beneficial in terms of required magnetic force from the actuator and breadth of range of engine that can be effectively serviced with a single design. Taken together, these attributes of a disk-valve closure can provide increased design efficiency and effectiveness and, more importantly, reduce overall cost.
An important negative attribute of disk valving, however, particularly when a gaseous medium such as natural gas or hydrogen is metered, is leakage propensity. As a disk-valve injector generally employs relatively low lifts, compared to an equivalent flow ball-valve injector, very high flow/seal areas are required to satisfy necessary engine flow capacity. The relatively large seal area creates high sensitivities to surface imperfections and goodness-of-fit and contamination, with the slightest mismatch between disk and seat resulting in intolerable leak rates. Consequently, disk-valve fuel injectors have not enjoyed widespread use in automotive engine applications, especially in the nascent domain of gaseous fuels.
What is needed in the art is an improved disk-valve fuel injector wherein the propensity for leakage, especially with gaseous fuels, is reduced.
It is a principal object of the present invention to provide an improved fuel injector suitable for use with both liquid and gaseous fuels in internal combustion engines.